According to this presentation, a legal entity that does not have a complete board (Verwaltungsrat) does not have the ability to conduct business. There is then a 30 day time period to correct the situation after the resignation appears in the commercial register, granted by the commercial register office. If this time period is not held to, then the court must decide how to proceed. Possible actions include:
1. Court grants a new time period to comply under the threat of liquidation of the company.
2. Court appoints a new board member to the board or representative (Sachwalter) to supervise the company.
3. Court orders the liquidation of the company according to bankruptcy regulations.
See pp.24-25: http://www.rwi.uzh.ch/lehreforschung...tationacht.pdf
Please don't misconstrue this reading of a presentation to be legal advice. If you need Swiss legal advice, contact a Swiss attorney.